The present invention relates to a bandgap reference (BGR) circuit. In particular, the present invention relates to a sub-1 V BGR circuit.
In a prior art sub-1V BGR circuit, elements such as op-amps, diodes, and resistors are implemented. These elements are fabricated as individual separate structures that work together as the sub-1V BGR circuit. Each element of the sub-1 V BGR circuit, as an individual structure, needs to be separated somewhat from the other elements of the sub-1V BGR. As such, the area occupied by the sub-1V BGR circuit cannot be accounted for merely by the elements themselves, but must additionally be accounted for by the extra spaces separating these elements.
Referring now to FIG. 1, a side sectional view of a resistor-diode series 110 implemented in a prior art sub-1V BGR circuit 100 is shown. Sub-1V BGR circuit 100 includes two portions 120 and 140. Portion 120 includes a resistor 121, while portion 140 includes a diode 141. Together, portions 120 and 140 include resistor-diode series 110 that is a part of sub-1V BGR circuit 100.
Referring still to FIG. 1, Resistor 121 and diode 141 as shown are individual and separate structures. As an individual structure, resistor 121 needs to be separated somewhat from diode 141. As such, the area occupied by sub-1V BGR circuit 100 cannot be accounted for merely by resistor 121 and diode 141 themselves, but must additionally be accounted for by the space between resistor 121 and diode 141.
Problematically, in typical applications (e.g., in an embedded system or in a system on-a-chip design), available chip real estate becomes so precious that the sub-1V BGR circuit occupies more area than desired. Furthermore, the resistance of the prior art sub-1V BGR circuit is difficult to control. To improve control of the resistance using conventional approaches, the standard process flow needs to be severely modified, thereby decreasing throughput in the fabrication process.
Thus, a need exists for a sub-1V BGR circuit that does not occupy as much space as the prior art sub-1V BGR. Additionally, a need exists for a sub-1V BGR that provides better control of the resistance for the resistor included therein. Further still, a need exists for a sub-1V BGR that is manufacturable using the process flow typically used in forming a standard semiconductor device, while not perturbing the process flow.
The present provides a sub-1V BGR circuit that does not occupy as much real estate as the prior art sub-1V BGR. Additionally, the present invention provides better control of the resistance for the resistor within the sub-1V BGR. Further still, the present invention provides a sub-1V BGR that is manufacturable using the process flow typically used in forming a semiconductor device, while not perturbing the process flow. As an additional benefit not available in the prior art sub-1V BGR circuit, the present invention provides a sub-1V BGR circuit without requiring complex structures.
Specifically, rather than having separate structures, the present invention provides a sub-1V BGR circuit as a single structure. The resistance of a resistor within this sub-1V BGR circuit is easier to control as compared to the resistance of a resistor within a conventional sub-1V BGR circuit. Also, the present invention provides a sub-1V BGR circuit that, in one embodiment, consumes approximately 14xc3x97 less real estate than is consumed by a conventional sub-1V BGR circuit.
In one embodiment of the present invention, the sub-1V BGR circuit comprises a shallow trench isolation (STI) region and a poly silicon region above said STI region. The poly silicon region as one single structure is adapted to function as a resistor and a diode coupled in series. Specifically, the structure is adapted to generate current in a feedback loop to provide a BGR voltage.